Sensors are used for determining a position, especially an absolute position, e.g. a machine axis or the like, for example in a machine tool, production machine and/or a robot. In such cases commercially available sensors for detection of the location, i.e. the position, feature a measuring element which can be present as a linear element or as a rotational element, with the measuring element having one or more tracks with a respective material measure in the form of increments, which are scanned by sensors for determining the position.
European patent application 0 116 636 discloses sensor, in which an absolute position is determined using a so-called PRBS track, featuring increments in the form of “zeros” and “ones”. An additional fine resolution of the absolute position is undertaken using a detection of the position of the transitions between the increments. In this case the disadvantage arises of on the one hand additional sensor systems being needed for detecting the transitions and on the other hand of eight or more sensors usually being needed for determining the position.
European patent application 0 503 716 discloses a sensor for determining an absolute position, with an absolute track and an incremental track being combined as a material measure to form a single composite track, with the absolute track being design such that its individual increments are distributed pseudo-randomly In this case the disadvantage is that eight or more sensors are usually needed to be able to determine the position.
A length measurement system is known from EP 0 530 176 A1, in which an incremental track and an absolute track are used as a material measure for determining a position, with the absolute track being used for the rough detection of the position and the additional evaluation of the incremental track finally delivering a more precise position value.
The basic principle of a sin/cos sensor is known from German application 27 29 697.
Known from German patent applications 10 2004 004 099 and 10 2004 004 100 are position sensors for detecting the position of a rotation body and corresponding measurement methods. Known from DE 10 2004 062 278 is a measuring element with a track, with the track having a material measure which is sampled by at least two sensors for determining a position, with the material measure being embodied such that the sensors output as their respective output signal a modulated sine-wave track signal for determining the position.
A rotary sensor for a combination drive is known from the German publication “Drehsensor für einen Kombinationsantrieb (Rotary sensor for a combination drive”, www.ip.com, IPCOM000028605D, Christoph Nolting, Hans-Georg Köpken, Günter Schwesig, Rainer Siess.
An absolute value encoder is known from DE 41 23 722 which comprises a code plate with a single-track absolute value pattern, a first incremental pattern with a first period and a second incremental pattern with a second period, with the smallest read unit of the single track absolute value pattern corresponding to the first period and the second period by a factor which is an integer power of two, is smaller than the first period. A detector section is movable relative to the code plate and contains a device for detecting the absolute value pattern in order to create an absolute value sample signal. With a device for detecting the first incremental pattern a first incremental pattern signal is created and with a device for detecting the second incremental pattern a second incremental signal is created. A shorter incremental sample signal in the cycle is generated by interpolation from the first incremental sample signal and this is synchronized with the second incremental sample signal. The absolute value sample signal, the second incremental sample signal and the synchronized first incremental sample signal represent the relative position relationship between the code plate and the detector section.
Furthermore a position-encoded sensor is known from 89/11080, in which for creation of a position-encoded signal at any time, two tracks are sampled by means of two sensors, which each create a sine-wave signal pair or a similar periodic signal with a phase position defined at any time, the period length of which behaves as m/(m−1), so that a sought relative distance is produced from a difference between the two phase positions.
Finally reference is also made to the prior art in the German publication entitled “Verfahren und Vorrichtung für Positionsmessung mit mehr als zwei Sensoren (Method and facility for position measurement with more than two sensors)”, www.ip.com, IPCOM000035541D, Roland Finkler, Hans-Georg Köpken, to which particular reference will be made later in this application.